In a 61-year-old woman with chronic left lower quadrant pain, nausea, constipation, negative ultrasound, negative fecal immunochemical test, negative celiac and Helicobacter pylori work‑up, normal labs, and persistent symptoms after hysteroscopic removal of uterine polyps, could the diagnosis be something other than irritable bowel syndrome?

Differential Diagnosis Beyond IBS in a 61-Year-Old Woman with Persistent Left Lower Quadrant Pain

Yes, several important diagnoses must be excluded before accepting IBS as the final diagnosis in this 61-year-old woman, particularly given her age over 50 years, which is itself an alarm feature requiring more thorough evaluation. 1, 2

Critical Age-Related Considerations

• Age >50 years is an alarm feature that mandates colonoscopy to exclude colorectal cancer and other structural pathology, regardless of negative fecal immunochemical testing. 1, 2
• The British Society of Gastroenterology explicitly states that advancing age warrants greater caution in diagnosing IBS due to increasing incidence of organic diseases with similar symptoms. 1
• Fecal immunochemical testing alone is insufficient to exclude colorectal pathology in patients over 50 with new or persistent symptoms. 2

Essential Diagnostic Workup Still Required

Mandatory Investigations

• Colonoscopy with biopsies is the single most important missing test in this patient, given her age and persistent symptoms despite negative basic workup. 3, 2, 4
• Complete blood count to assess for anemia (which may not be detected by fecal immunochemical test alone). 2, 5, 4
• C-reactive protein or erythrocyte sedimentation rate to identify inflammatory processes. 3, 5, 6
• Fecal calprotectin to distinguish inflammatory bowel disease from functional disorders (more sensitive than fecal immunochemical test for inflammation). 3, 7, 6

Imaging Considerations

• CT abdomen and pelvis with IV contrast should be obtained if there is diagnostic uncertainty, particularly to evaluate for diverticulitis, masses, or other structural pathology in the left lower quadrant. 3
• The absence of fever and leukocytosis makes acute diverticulitis less likely, but chronic or smoldering diverticular disease remains possible. 3

Key Differential Diagnoses to Exclude

Gynecologic Causes (Despite Prior Hysteroscopy)

• Endometriosis can cause left lower quadrant pain and bowel symptoms and would not be detected by hysteroscopy, which only evaluates the uterine cavity. 1
• Ovarian pathology (cysts, masses) requires pelvic ultrasound or CT imaging for evaluation.
• Adhesions from prior hysteroscopy could cause chronic pain and altered bowel function. 1

Gastrointestinal Pathology

• Colorectal cancer must be excluded via colonoscopy in any patient over 50 with new or persistent lower abdominal symptoms. 2, 5
• Inflammatory bowel disease (particularly Crohn's disease or microscopic colitis) can present with left-sided pain and constipation; requires colonoscopy with biopsies. 2, 7
• Diverticular disease (chronic or segmental colitis) is common in this age group and can cause persistent left lower quadrant symptoms. 3
• Chronic constipation with defecatory disorder (pelvic floor dysfunction) should be evaluated with digital rectal examination during simulated defecation. 1, 4

Other Considerations

• Celiac disease has already been appropriately excluded. 5
• Bile acid diarrhea can paradoxically present with constipation in some patients and should be considered if diarrhea develops. 4

Why IBS Diagnosis Is Premature

• IBS is a diagnosis of exclusion that requires ruling out structural and biochemical abnormalities, which has not been adequately done without colonoscopy in a patient over 50. 1, 8, 5
• The Rome II criteria require at least 12 weeks of symptoms with specific features (pain relieved by defecation, change in stool frequency, change in stool form), and it's unclear if this patient fully meets these criteria. 1
• The presence of nausea suggests possible overlap with functional dyspepsia or upper gastrointestinal pathology, which occurs in 42-87% of IBS patients but may indicate a different primary diagnosis. 1

Recommended Diagnostic Algorithm

1. Perform colonoscopy with biopsies immediately - this is the highest priority missing investigation. 3, 2, 4
2. Obtain inflammatory markers (CRP or ESR) and fecal calprotectin before colonoscopy. 3, 5, 6
3. Perform digital rectal examination with assessment of pelvic floor function during simulated defecation to evaluate for defecatory disorders. 1, 4
4. Consider CT abdomen/pelvis if colonoscopy is delayed or if symptoms suggest structural pathology. 3
5. Only after negative colonoscopy and exclusion of organic disease should IBS be diagnosed using Rome criteria. 1, 5

Common Pitfalls to Avoid

• Do not diagnose IBS in patients over 50 without colonoscopy - this is the most critical error and can lead to missed colorectal cancer. 1, 2
• Do not assume hysteroscopy excluded all gynecologic causes - endometriosis, ovarian pathology, and adhesions require different imaging. 1
• Do not rely solely on fecal immunochemical testing - it has limited sensitivity for right-sided lesions and inflammatory conditions. 2
• Do not overlook defecatory disorders - these require specific physical examination techniques and do not respond to standard IBS treatments. 1, 4